let app = new Vue({
	el: '#app',
	data: {
		math: 90,
		physics: 80,
		english: 30
	},
	computed: {
		sum: function () {
			return this.math + this.physics + this.english;
		},
		average: function () {
			return Math.round(this.sum / 3);
		}
	}
})